HIV rates have increased substantially for the first time in five years, leading experts to warn that urgent action is needed to stop the spread of the virus.
Figures released today show that the number of new diagnoses increased by 8 per cent last year, and by 50 per cent during the past 10 years.
David Wilson, the head of the Kirby Institute's surveillance and evaluation program for public health at the University of NSW, said NSW, Victoria and the ACT had driven the increase.
''In these three states we have seen quite a significant rise in the last calendar year,'' he said.
Victoria experienced the biggest increase but in NSW more people were being picked up with HIV they had contracted only recently, as opposed to being picked up only after the condition had progressed.
Associate Professor Wilson said it was unusual for infectious diseases such as HIV to increase after they had been controlled but the lowest levels of HIV diagnosis in Australia were 10 years ago. ''We thought we had at least reached a plateau about five years ago but we have not,'' he said.
About 24,000 to 25,000 Australians live with diagnosed HIV but up to 10,000 might not have been diagnosed, he said.
The most recent increase in the number of new HIV cases diagnosed - from 1051 in 2010 to 1137 in 2011 - has been driven by increases among gay men, although in the past 10 years there have been rises in other groups.
John de Wit, the director of the National Centre in HIV Social Research at the University of NSW, said research indicated a small increase in unprotected sex among gay men, with more than one-third reporting unprotected sex with a casual partner in the past six months. But this increase probably did not explain the entire rise in diagnoses, and nor did increases in testing.
Experts attending the Australasian HIV/AIDS Conference today will launch a plan, the Melbourne Declaration, in an attempt to stop the spread of the disease.
The president of the Australasian Society for HIV Medicine, Edwina Wright, said the declaration included calls to remove restrictions on funding for medications for people in the early stages of the disease and speed up the approval of antiretroviral drugs for the prevention of HIV in people exposed to it.
The executive director of the Australian Federation of AIDS Organisations, Rob Lake, said the increase in diagnoses was a call to action.
He said Australia must urgently introduce rapid HIV testing, for which a licence had not yet been granted.
Rapid testing gives a result within an hour, rather than a week, and so reduced the time people were unaware of their infection, he said.
HIV rates in Australia skyrocketed in the late 1980s, increasing from 400 new cases in 1984 to a peak of nearly 2400 new cases in 1987, after which numbers declined for more than 10 years.
But at the turn of the century, the number of new infections started to creep up each year, although HIV experts had believed the fairly steady numbers during the past five years indicated there would be no further increases.